\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=latex,scale=1]
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  \draw [thick](-2,1)--(-2,.5);
  \draw (0,0)--(-2,.75);
  \draw (0,0)--(2,1);
  \draw [thick,->](0,0)--(-1,.75/2)node [below]{$F$};
  \draw [thick,->](0,0)--(1,1/2)node [below]{$F$};
  \draw [thick,->] (1.75,1.4)--node [above]{$a$} (2.5,1.4);
  \draw (0,0)--(0,-1);
  \draw (-0.25,-1) rectangle(.25, -1.8);
  \draw [thick,->](0,-2.8/2)--(0,-2.5) node [right]{$G=mg$};
  \draw (1/2,1/4) arc  (30:160:.56);
  \node at (0,.25){$\alpha$};
\end{tikzpicture}
\end{document}